Methods of preparing flotation reagents



Patented Feb. 16, 1954 METHODS OF PREPARING FLOTATION REAGENTS FrederickR. Archibald, Toronto, Ontario, Canada, assignor to United States SteelCorporation, a corporation of New Jersey N Drawing. Application July 5,1951, Serial No. 235,359

Claims.

This invention relates to improved methods of preparing flotationreagents which consist essentially of collectors of the fatty acid typeand colloidal silica and are substantially free of alkali metal ions.

My co-pending application Serial No. 172,197, filed July 5, 1950,describes and claims the foregoing type of reagents and also flotationmethods involving their use. Briefly these reagents consist of about0.06 to 0.6 part by weight of colloidal silica to one part by weight ofa collector of the fatty acid type on an anhydrous basis; they have amol ratio of silica to alkali metals of at least 25 to 1; preferablythey are premixed. These reagents are particularly useful for floatingiron oxide minerals from siliceous gangue, where colloidal silica is ahighly effective agent for wetting and depressing gangue particles andallowing the collector to float the iron oxide mineral particles.

My aforesaid application defines collectors of the fatty acid type asincluding higher fatty acids, such as oleic acid, palmitic acid,linoleic acid, lauric acid, myristic acid, stearic acid and tariricacid; esters of the higher fatty acids, such as their glyceryl andglycol esters; resin acids, such as abietic acid, naphthenic acids; andvarious mixtures of the foregoing, but in each instance beingsubstantially free of ions of alkali metals such as would be found inthe sodium salts of the various acids. In the present application thissame definition applies, but I also define "fatty acid material asincluding all the foregoing substances, as well as their alkali metalsoaps. As sources of fatty acid materials, I prefer crude mixtures offatty acids and resin acids, such as tall oil, which is sold under thetrade names Opoil and Facoil, crude soap skimmings from the pulp andpaper industry, or cottonseed foots, all of which have the advantages ofready availability and low cost.

An object of the present invention is to provide preparation methodswhich produce improved pre-mixed reagents in which collectors of thefatty acid type and colloidal silica of low alkali metal content aremore highly dispersed, and which reagents have enhanced wetting actionon siliceous mineral particles.

A further object is to provide simplified and improved methods ofpreparing such reagents in which preferably the components are pro-mixedand treated with an ion exchange medium to remove alkali metal ions,although without sacrificing all the benefits of the invention, thesecomponents can be treated separately with the ion exchange medium andeither subsequently mixed or added separately to an ore pulp.

According to the preferred way of practicing the present invention, afatty acid material first is mixed with sodium silicate. Said fatty acidmaterial can be any of those previously mentioned. An example is Opoilin which the fatty acids are chiefly oleic, linoleic and palmitic andthe resin acid chiefly abietic. The fatty acid content is about 46 to48.5% and the resin acid content about 42.2 to 45% (calculated asabietic). The sodium silicate can be any of the commercially availablepreparations. Such preparations commonly have a mol ratio of SiOz toNazO of about 3.2 to 1, a specific gravity of about 40 to 43 Baum, and.contain roughly 30% S102. An example is Philadelphia Quartz Company Nbrand. The proportions used are equivalent to about 0.06 to 0.6 part byWeight of SiOz to 1 part by weight of collector of the fatty acid typeas produced in .the subsequent ion exchange reaction. Many of the fattyacid materials, such as the soaps, are readily dispersed in sodiumsilicate solution without additional dispersing agents, but whereneeded, as With the acids themselves, alkali or ammonium hydroxide canbe added either in this first mixing step, or previously to the fattyacid, to act as a dispersing agent.

Next the mixture is diluted with water and roughly emulsified to form asolution having a maximum S102 content of about 1.5%. In the example ofOpoil and N brand sodium silicate, if the solution is diluted to 1%Opoil, the maximum concentration of N brand sodium silicate (30% SiOz)is about 5%, or if the solution is diluted to 1% N brand sodiumsilicate, the maximum concentration of Opoil is about 5%, to producesatisfactory reactions with the ion exchanger. The actual proportionsused give the ratio of 0.06 to 0.6 part by weight of SiOz to 1 part byweight of collector of the fatty acid type in the finished reagent,these maximum concentrations being merely those that reactsatisfactorily with the ion exchanger.

Next the solution thus prepared is treated with an acid type ionexchange medium. This medium can be of any of the Well known substanceswhich are capable of exchanging hydrogen ions for sodium ions present inthe sodium silicate, in the fatty acid material, and in the dispersingagent if used. Examples of such substances are natural and syntheticzeolite and certain synthetic resins which have hydrogen atoms in ionexchange positions, such as the phenolic resin sold by the trade nameAmberlite lR-lOOH. Either the solution can be passed through a bed ofion exchanger or else granules of the exchanger can be agitated with thesolution. During such treatment the ion exchanger acquires alkali metalions from the solution, but can be regenerated by treatment with anacid, as known in the art.

ti'oduce additional colloidal silica to the resulting product. Thispractice is particularly useful where the desired ratio of colloidalsilica to collector is higher than desired for treatment with Theeffluent from the ion exchange is a highly 5 the ion exchanger.dispersed solution of colloidal silica and collector Specific examplesof ways in which reagents of the fatty acid type and has a very lowcontent can be prepared according to the present invenof alkali metalions, that is, a mol ratio of silica tion and used in flotationprocesses are as folto alkali metals of at least 25 to 1. The pH of thelows: original solution varies from to 12 and that of 10 the effluentfrom 2.5 to 3.5. The solution can be EXAMPLE I stabilized by addition ofa small amount of so- 10 ram ofcrude tall oil (Opoil) was mixed diumsilicate as long as the alkali metal ion con- Wi h 10 gr ms of sodiumsilicate solution (Philatent is maintained within the limitshereinbefore delp Quartz p y. N brand). The mixstated. This solution canbe used as a flotation 15 t was diluted with a little water, warmed onreagent in the manner described and claimed in a hot plate, and shakenuntil roughly emulsified. my aforesaid application; that is, it can bemixed T miXture W d uted to 1 liter with Water with a. finely dividedpulp of iron oxide ore and and stirred With an electric stirrer untilunisiliceous gangue, which then can be treated in formly mixed. Next itWas Passed through a any standard or desired flotation cell. The 001-acid p n h n lumn and the r sultin loidal silica effectively wets anddepresses the Product Was a milky l d mu siongangue, while the collectorof the fatty acid type A samp of classifier lmderfiOW from a Closedfloats the iron xide minerals circuit grinding and classificationoperation on Pro-mixing the components before treating taconite ore wasselected for treatment. A rethem with the ion exchanger produces a moreagent p p as j t de c bed was added to highly dispersed and activereagent than when the Sample in an amount equivalent to Pound thecomponents are mixed after s ch t t t tall oil and 0.81 pound sodiumsilicate solution or added separately to an ore pulp. While I do(approximately p d Co lo al Sil ca On an not wish to limit myself to anyparticular theory, enhydrells basis) D Ions ten o olids in the I believethis improvement is due at least in part Sample In accordance With thethird p s il ty to the formation of the colloidal silica in thedescribed hereinbefore, addit o al colloidal silica presence of fattyacid ions. According to this was introduced an nt qu v l nt t 1 theory,the wetting action of colloidal silica on p nd um s i t ti n appr x atly siliceous gangue is due partially to its afiinity to 0.25 poundcolloidal silica on an anhydrous basis) calcium ions which usually areassociated with D i; ten of SelidS- After pp p mixing this gangue. Fattyacid ions are known to have the sample was tr d y fleatiel'l and O astrong affinity for calcium ions. Colloidal silica the samp Weight arecovered as a flotation molecules which are formed in the presence ofConcentrate a say n 3.5% Fe and 6.0% acid infatty acid molecules tend toconform in physcial soluble residue. This concentrate was recoverdstructure to the latter and consequently acquire 40 at a much coarserparticle size and a higher some of the affinity of fatty acid ions forcalcium grade than was being obtained in the regular ions, becoming ineffect tailor-made molecules. opertion after grinding much finer andusing Some of the benefits of the present invention magnetic separatorsfor treatment of classifier can be achieved by treating a fiatty acidmaterial overflow. Screen analyses and grades of concenalone with anionic exchanger and then either trates obtained by flotation of theclassifier unmixing it with previously prepared colloidal silica derfiowand magnetic separation of the clasifier or adding the two separately toan ore pulp. In overflow were as follows:

Magnetic Flotation, Mesh Sue tiiigiii (figfixg Separator Concentrate66323; Cumulative Fe Insol Fe/Insol Fe Insol Fe/lnsol i l iatir'f'. -991 4 7- 9-! this instance the fatty acid material can be any of EXAMPLEII those previously mentioned, and it is treated in concentrations up to20% with any of the same ionic exchangers. This alternative way ofpracticing the invention retains the benefits of substantiallyeliminating alkali metal ions and of producing a highly dispersedcollector of the fatty acid type, but of course it loses the advantagesgained by forming the colloidal silica in the presence of fatty acid.

A third possibility is to pre-mix the fatty acid material and sodiumsilicate and treat them together with the ion exchanger, as in thepreferred practice already described,- and then to in- The fatty acidmaterial was soap skimmings, a by-product of the pulp and paper industrycontaining alkali metal compounds of fatty and resin acids, as well asother degradation products of pulp wood and inorganic salts incidentalto the manufacturing process. 10 grams of soap skimmings were mixed withone liter of colloidal silica solution containing the silica equivalentof 10 grams of N brand sodium silicate. The mixture was stirred with amotor stirrer until thoroughly dispersed and then passed through an acidtype ion exchange medium set up as a column in a glass tube. Theeffluent was used as a flotation reagent in the manner next described.

A sample of iron ore classifier underflow containing approximately 1300grams of solids and representing the circulating load in a grinding andclassification circuit was placed in a laboratory flotation cell andconditioned with 100 ml. of the efliuent thus prepared for 6 minutes.The pulp was diluted to the normal operating level and froth removed.The rougher concentrate was returned to the cell and twice re-cleaned,producing a cleaner concentrate assaying 65.25% Fe and 5.64% acidinsoluble residue, equal in weight to 30.8% of the original sample. Thereagents used were equivalent to 1.74 pounds each of soap skimmings andsodium silicate solution (0.52 pound of colloidal silica on an anhydrousbasis) per long ton of solids.

For comparison, to show the advantage of premixing the fatty acidmaterial and sodium silicate and treating them together with the ionexchanger, a similar ore sample was treated by flotation with theseagents prepared by separate treatment with an ion exchanger. Otherconditions were identical. This treatment yielded 28% of the weight ofthe sample as a concentrate assaying 64.05% Fe and 6.2% acid insolubleresidue.

From another sample of classifier underflow taken under differentoperating conditions and using the pre-mixed reagent of the presentexample, 42.8% of the sample weight was recovered as a concentrateassaying 65.85% Fe and 5.66% acid insoluble.

EXAMPLE III For comparative tests two reagents were prepared similarlyexcept that the first lacked treatment with an ion exchanger. This firstreagent was prepared by mixing 1 gram of ammonium hydroxide with gramscrude tall oil, warming and then diluting to one liter. 10 grams N brandsodium silicate was diluted with water to a volume of 1 liter. Equalvolumes of ammoniatall oil and diluted sodium silicate were mixed andproduced a cloudy and somewhat viscous solution. The second reagent wasprepared by passing some of this same solution through an acid type ionexchange medium. I

For comparison of the effectiveness of the two reagents, a sampleclassifier underflow as described in Example I was divided into two portions containing approximately 800 grams of solids each. In eachflotation test the pulp was added to a laboratory flotation cell andconditioned with 150 ml. of reagent solution. Flotation and onere-cleaning were carried out on each utilizing the two reagents preparedas described, following usual procedures and without further reagentadditions. The results were as follows:

Percent Analysis Concentrate Weight as Concentrate Fe Inso] Fe/InsolFirs Reagent 46. 5 61.35 7. 94 7.73 Second Reagent 46. 6 64.05 6. 3010.17

6 EXAMPLE IV 10 grams of soap skimmings were diluted with stantially alldissolved or dispersed. The mixture was run through an acid type ionexchanger set up in a vertical glass tube 2 inches in diameter. Thecolumn of ion exchange resin (Amberlite 1R-100H) was 15 inches high. The

effluent from the exchanger was used as a flotation collector inconjunction with colloidal silica having a mol ratio of silica to alkalimetal ions of at least 25 to 1.

A sample of classifier underflow pulp was taken from a closed circuit asin the preceding examples and split to give representative portions ofabout 1360 grams of solids each. One such portion was placed in alaboratory flotation cell and conditioned with 50 m1. colloidal silicasolution for three minutes. The colloidal silica solution containedsilica equivalent to approximately 3 grams $102 per liter. '75 ml. ofthe fatty acid collector next was added and conditioning carried on forfive minutes more. The pulp level was raised to normal operating levelby addition of water. Froth was removed for 5 minutes. The rougherconcentrate thus obtained was returned to the cell using the originalflotation liquor for dilution, and again froth was removed in the usualWay. One more re-cleaning was performed in the same manner. The totalreagents used were equivalent to 1.30 pounds soap skimmings and 0.86pound sodium silicate (0.26 pound silica on an anhydrous basis) per longton of ore. The sodium silicate had been converted to colloidal silicasolution by passing diluted water glass through an acid type ionexchanger. The flotation resulted in a recovery of 33.4% of the weightof the sample in a concentrate assaying 64.65% Fe and 6.54 acidinsoluble residue.

EXAMPLE V A similar sample of classifier underflow was treated byflotation with the same reagents in larger quantities, namely, theequivalent of 2 pounds of soap skimmings and 1 pound sodium silicate(0.30 pound silica on an anhydrous basis) per long ton of ore. By onere-cleaning of the rougher concentrate, 59.1% of the total sample weightwas recovered in a product assaying 63.8% Fe and 7.24% acid insoluble.

From the foregoing description it is seen that the present inventionaffords a simple method of preparing a highly effective reagent forfloating iron ore minerals from siliceous gangue. As best shown by thecomparative tests of Example II, reagents in which the fatty acid typematerial and sodium silicate are mixed together before treatment withthe ionic exchanger produce better results than reagents in which thetwo are separately prepared, although the latter still are effectivereagents.

While I have described only certain preferred ways of practicing theinvention, it is apparent that modifications may arise. Therefore, I donot wish to be limited by the specific disclosure, but only by the scopeof the appended claim.

I claim:

1. A method of preparing pre-mixed flotation reagents, which consistessentially of collectors of th fatty acid type and colloidal silica inproportions of about 0.06 to 6.6 parts by weight of colloidal silica toone part by weight of collector on an anhydrous basis and have a molratio of silica to alkali metals of at least 5 to 1, comprising treatingsodium silicate and an alkali 7 metal soap of an acid ofuthe groupconsisting of higher fatty acids, resin tion, with an acid type ionexchange medium which removes alkalimetal ions therefrom.

2. A method as defined in claim 1 in which the dilute water solutions ofsoap and sodium silicate are mixed together before treatment with theion exchange medium.

3. A method. as defined. in claim .1 in which the dilute. watersolutionsof soap and sodium silicate ar treated separately with the ioneX- change medium and subsequently mixed.

4. A method of preparing pre-mixe'd flotation reagents, which consistessentially of collectors of the fatty acidtype and colloidal silicainproportions of about 0.06 1100.6. parts-by Weight of colloidal silicavto one ,part by weight of collector. on an anhydrous basis and have amol ratio of silica to alkali metals of at least 25. to 1, comprisingmixing .water solutions of .sodium silicate and an alkalimetal. soap ofan acid of.

acids, naphthenic acids. and mixturesthereof, both,indilute,watersoluthe group consisting of higher fatty acids, resin acids,naphthenic acids. and mixtures thereof, di-

luting the mixture with water to a maximum thenicacids and mixturesthereofpand thus removing alkali metal ions therefrom.

FREDERICK "R. ARCHIBALD.

References Cited' in the file of thispatent UNITED. STATES PATENTSNumber Name Date 1,326,855 Edserv Dem 30, 1919v 1,492,904 1Sulman'et-al; May 6; 1924 3,164,063 -..-Handy l June 27, 1939 OTHERREFERENCES NachodIon Exchange-pub. 1949 by AcademicPress of N. Y-.-p.365 copyinDiv. .63.

an acidof, the group consisting of higher fatty acids, resin acids,naph-

1. A METHOD OF PREPARING PRE-MIXED FLOTATION REAGENTS, WHICH CONSIST ESSENTIALLY OF COLLECTORS OF THE FATTY ACID TYPE AND COLLOIDAL SILICA IN PROPORTIONS OF ABOUT 0.06 TO 0.6 PARTS BY WEIGHT OF COLLOIDAL SILICA TO ONE PART BY WEIGHT OF COLLECTOR ON AN ANHYDROUS BASIS AND HAVE A MOL RATIO OF SILICA TO ALKALI METALS OF AT LEAST 25 TO 1, COMPRISING TREATING SODIUM SILICATE AND AN ALKALI METAL SOAP OF AN ACID OF THE GROUP CONSISTING OF HIGHER FATTY ACIDS, RESIN ACIDS, NAPHTHENIC ACIDS AND MIXTURES THEREOF, BOTH IN DILUTE WATER SOLUTION, WITH AN ACID TYPE ION EXCHANGE MEDIUM WHICH REMOVES ALKALI METAL IONS THEREFROM. 